1. Field of the Invention
The present invention relates to a chip mounting technique, and more particularly to a technique which can be used effectively for mounting chip type electronic parts such as semiconductor pellet.
2. Related Art Statement
Typically, chip parts such as chip type electronic parts including semiconductor devices, resistors and capacitors are sucked with a suction bit of a chip mounter and then mounted onto a lead frame etc.
For example, as a chip mounter used in such a mounting technique, a chip mounter which is provided with an image processing system for recognizing as an image a chip sucked by a suction bit has been well known.
A chip mounter with such an image processing system recognizes whether a chip is sucked in a predetermined proper position of a suction bit or not by the image processing system. If the chip is not sucked at a predetermined proper position, the position is adjusted to the predetermined position of the chip based on a resultant image recognition by the image processing system.
Now, in the aforementioned chip mounter provided with an image processing system, the periphery of the suction bit is recognized as a background of a chip by the image processing system, and is formed with milk-white semitransparent resin and the like. Thereby, illumination light from a light emitting diode and the like permeates the resin and then strikes into an optical lens of the image processing system.
However, since at least the tip surface side, i.e. suction surface side of the suction bit, is formed of a metal, when the suction bit sucks the chip while its tip surface side is positioned within a chip surface to be sucked, the image processing system can recognize properly the chip as a proper image. However, when the suction bit sucks the chip while its tip surface side deviates from the chip surface area to be sucked, the image processing system recognizes the tip surface side of the suction bit as a dark shaded image which is the same as that produced by the chip.
As a result, the image processing system may recognize erroneously the shape image of the chip, whereby there is a danger that adjusting the position of a chip based on the image recognition by the image processing system becomes impossible.